Motor control system and motor control method

Abstract

To reduce the processing load related to motor control while maintaining a constant motor rotation speed. [Solution] The motor control system 100 comprises a first acquisition unit 51, a calculation unit 52, and a control unit 53. The first acquisition unit 51 acquires pulses output by a detection unit 91 that detects the rotational speed of a motor 92 that rotates a transport body (screw) for transporting toner to be removed. The calculation unit 52 calculates the rotational speed of the motor 92 based on the acquired pulses at a specific period longer than the pulse period. The control unit 53 controls the motor 92 so that the rotational speed of the motor 92 remains constant based on the rotational speed calculated by the calculation unit 52.

Description

Technical Field

[0001] The present invention relates to a motor control system and a motor control method.

Background Art

[0002] As a related art, there is known an image forming apparatus in which the driving load of a motor power control unit that transmits a driving force to a waste toner conveying member increases as the amount of toner in a waste toner collection container increases (for example, see Patent Document 1). In this image forming apparatus, when the switching timing arrives, the motor power control unit switches the driving control of the motor from a continuous driving mode in which the motor is continuously driven to an intermittent driving mode in which the driving and stopping of the motor are repeated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above related art, it does not have a function of controlling the rotational speed of the motor, and only controls the driving or stopping of the motor to switch between the continuous driving mode and the intermittent driving mode. For this reason, in the above related art, there is a problem that the amount of toner recovered per unit time decreases in the intermittent driving mode, and the toner is likely to be clogged.

[0005] In order to solve the above problem, it is conceivable to control the rotational speed of the motor to be constant, but there is a problem that the processing load related to the control of the motor tends to increase.

[0006] The object of the present invention is to provide a motor control system and a motor control method that can easily reduce the processing load related to motor control while maintaining a constant motor rotation speed. [Means for solving the problem]

[0007] A motor control system according to one aspect of the present invention comprises a first acquisition unit, a calculation unit, and a control unit. The first acquisition unit acquires pulses output by a detection unit that detects the rotational speed of a motor that rotates a transport body for transporting toner to be removed. The calculation unit calculates the rotational speed of the motor based on the acquired pulses at a specific period longer than the period of the pulses. The control unit controls the motor based on the rotational speed calculated by the calculation unit so that the rotational speed of the motor remains constant.

[0008] A motor control method according to another aspect of the present invention includes an acquisition step, a calculation step, and a control step. In the acquisition step, pulses output by a detection unit that detects the rotational speed of a motor that rotates a transport body for transporting toner to be removed are acquired. In the calculation step, the rotational speed of the motor is calculated based on the acquired pulses at a specific period longer than the period of the pulses. In the control step, the motor is controlled based on the rotational speed calculated in the calculation step so that the rotational speed of the motor remains constant. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a motor control system and a motor control method that can easily reduce the processing load related to motor control while keeping the motor's rotational speed constant. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a schematic diagram showing the configuration of an image forming apparatus according to an embodiment. [Figure 2]Figure 2 is a schematic diagram showing the configuration of the cleaning apparatus of the image forming apparatus according to the embodiment. [Figure 3] Figure 3 is a block diagram showing the configuration of an image forming apparatus according to an embodiment. [Figure 4] Figure 4 shows an example of data referenced by the control unit of the motor control system according to the embodiment. [Figure 5] Figure 5 is a flowchart showing an example of the operation of the motor control system according to the embodiment. [Figure 6] Figure 6 shows an example of motor control using the motor control system according to the embodiment. [Figure 7] Figure 7 is a block diagram showing the configuration of an image forming apparatus according to a modified example of the embodiment. [Figure 8] Figure 8 is a flowchart showing an example of the operation of a motor control system according to a modified embodiment. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described below with reference to the attached drawings. The following embodiments are examples that embody the present invention and are not intended to limit the technical scope of the present invention.

[0012] [1] Overall configuration of the image forming apparatus First, the schematic configuration of the image forming apparatus 10 according to this embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic cross-sectional view of the image forming apparatus 10. Figure 2 is a schematic top view showing the configuration of the cleaning apparatus 36. In the following description, the arrows indicating direction in Figure 1 define up, down, left, and right. Also, in the following description, the front of the page is defined as the front of the image forming apparatus 10, and the back of the page is defined as the rear of the image forming apparatus 10. Of course, the above definitions of direction are not intended to limit the manner in which the image forming apparatus 10 is used.

[0013] In this embodiment, as an example, the image forming apparatus 10 is a multifunction device that has multiple functions, including a printer function for forming images based on image data, as well as a scanning function, a facsimile function, and a copying function. The image forming apparatus 10 may also be, for example, a printer, a facsimile, and a copier.

[0014] As shown in Figure 1, the image forming apparatus 10 includes an ADF 1, an image reading unit 2, an image forming unit 3, a paper feeding unit 4, a control device 5, an ejection unit 6 (see Figure 2), an operation display unit 7 (see Figure 3), and a storage unit 8 (see Figure 3), etc.

[0015] As shown in Figure 1, the ADF1 is an automatic document transport device comprising a document setting section 11, a plurality of transport rollers 12, a document holding section 13, and a paper discharge section 14. In the ADF1, each transport roller 12 is driven by a motor (not shown), so that the sheet placed on the document setting section 11 is transported through the image data reading position by the image reading section 2 to the paper discharge section 14. This allows the image reading section 2 to read image data from the sheet transported by the ADF1.

[0016] As shown in Fig. 1, the image reading unit 2 includes a document table 21, a reading unit 22, mirrors 23 and 24, an optical lens 25, and a CCD (Charge-Coupled Device) 26. The document table 21 is a placement part for sheets provided on the upper surface of the image reading unit 2. The reading unit 22 includes an LED light source 221 and a mirror 222, and is movable in the sub-scanning direction (here, the left-right direction) by a motor (not shown). The LED light source 221 includes a number of white LEDs arranged along the main scanning direction (here, the front-back direction). The mirror 222 reflects the light that is irradiated from the LED light source 221 and reflected by the surface of the sheet at the reading position on the document table 21 toward the mirror 23. Then, the light reflected by the mirror 222 is guided to the optical lens 25 by the mirrors 23 and 24. The optical lens 25 condenses the incident light and makes it incident on the CCD 26. The CCD 26 has a photoelectric conversion element or the like that inputs an electrical signal corresponding to the amount of received light of the light incident from the optical lens 25 to the control device 5 as image data of the sheet.

[0017] The image forming unit 3 is an electrophotographic image forming unit capable of executing an image forming process (printing process) for forming an image based on the image data read by the image reading unit 2. Also, the image forming unit 3 can execute an image forming process based on the image data input from an information processing device such as an external personal computer.

[0018] Specifically, as shown in Fig. 1, the image forming unit 3 includes a photosensitive drum 31, a charging device 32, an optical scanning device (LSU) 33, a developing device 34, a transfer roller 35, a cleaning device 36, a fixing roller 37, a pressure roller 38, and a paper discharge tray 39. In the image forming unit 3, an image is formed on the sheet supplied from a paper feed cassette 41 that is detachable from the paper feed unit 4 described later in the following procedure, and the sheet after image formation is discharged to the paper discharge tray 39. Note that the sheet is paper, coated paper, postcard, envelope, or OHP sheet, etc.

[0019] The operation of the image forming unit 3 will be specifically described below. First, the photoreceptor drum 31 is uniformly charged to a predetermined potential by the charging device 32. Next, light based on image data is irradiated onto the surface of the photoreceptor drum 31 by the optical scanning device 33. As a result, an electrostatic latent image corresponding to the image data is formed on the surface of the photoreceptor drum 31. Then, the electrostatic latent image on the photoreceptor drum 31 is developed (visualized) as a toner image by the developing device 34. Note that toner (developer) is supplied to the developing device 34 from a toner container 34A that is detachable from the image forming unit 3. Subsequently, the toner image formed on the photoreceptor drum 31 is transferred onto a sheet by the transfer roller 35. Thereafter, the toner image transferred onto the sheet is heated by the fixing roller 37 and melted and fixed when the sheet passes between the fixing roller 37 and the pressure roller 38.

[0020] On the other hand, the toner remaining on the surface of the photoreceptor drum 31 is removed by the cleaning device 36. Specifically, as shown in FIGS. 1 and 2, the cleaning device 36 includes a cleaning member 361, a polishing roller 362, and a screw 363. The cleaning member 361 is a blade-shaped member that removes the remaining toner adhering to the surface of the photoreceptor drum 31. The polishing roller 362 adheres the toner removed by the cleaning member 361 to its surface and polishes the surface of the photoreceptor drum 31. The screw 363 conveys the toner removed by the cleaning member 361 along the axial direction 31A of the photoreceptor drum 31 to a discharge unit 6 described later. Here, the screw 363 is an example of the carrier in the present invention.

[0021] The paper feeding unit 4 includes a paper feeding cassette 41 that is detachable from the apparatus main body of the image forming apparatus 10, and a plurality of conveying rollers 42. In the paper feeding unit 4, each conveying roller 42 is driven by a motor (not shown), and thus the sheet placed on the paper feeding cassette 41 is supplied to the image forming unit 3.

[0022] The control device 5 comprehensively controls the image forming apparatus 10. The control device 5 also functions as a motor control system 100, which will be described later. As shown in Figure 3, the control device 5 comprises a CPU 5A, a ROM 5B, and a RAM 5C. The CPU 5A is a processor that performs various arithmetic operations. The ROM 5B is a non-volatile memory device in which information such as control programs for instructing the CPU 5A to perform various operations is pre-stored. The RAM 5C is a volatile memory device used as temporary memory (work area) for the various operations performed by the CPU 5A.

[0023] In the control device 5, various control programs pre-stored in the ROM 5B are executed by the CPU 5A. As a result, the image forming apparatus 10 is comprehensively controlled by the control device 5, and the control device 5 functions as a motor control system 100. The control device 5 may be composed of electronic circuits such as an integrated circuit (ASIC). Furthermore, the control device 5 may be a separate control unit from the main control unit that comprehensively controls the image forming apparatus 10.

[0024] As shown in Figure 2, the discharge unit 6 is positioned to protrude axially 31A from the rear end of the housing of the cleaning device 36, corresponding to the position of the screw 363 in the cleaning device 36. Here, the screw 363 transports toner in the transport direction 363A, which is the same direction as the protrusion direction of the discharge unit 6. The tip of the screw 363 in the transport direction 363A extends to the discharge unit 6. Therefore, the toner removed from the surface of the photoreceptor drum 31 is transported to the discharge unit 6 by the screw 363. The toner transported to the discharge unit 6 is discharged through an outlet (not shown) of the discharge unit 6 into a toner container (not shown) that is detachable from the discharge unit 6.

[0025] The operation display unit 7 is the user interface of the image forming apparatus 10. The operation display unit 7 has a display unit such as a liquid crystal display that displays various information in response to control instructions from the control device 5, and an operation unit such as operation keys or a touch panel that inputs various information to the control device 5 in response to user operations.

[0026] The memory unit 8 is a non-volatile memory. For example, the memory unit 8 is a non-volatile memory such as flash memory and EEPROM (registered trademark), an SSD (solid state drive), and an HDD (hard disk drive).

[0027] Incidentally, in image forming apparatuses such as image forming apparatus 10, a configuration is known for recovering toner removed from the surface of the photoreceptor drum (in other words, waste toner or transfer residue toner). In this configuration, toner is transported to a toner collection container via a discharge unit by controlling a motor to drive a transport member (e.g., a screw). Here, a related technology is known in which, for example, when the amount of toner in the toner collection container increases, the motor drive control is switched from a continuous drive mode in which the motor is driven continuously to an intermittent drive mode in which the motor is repeatedly driven and stopped.

[0028] However, when the motor is driven intermittently, as in the related technologies mentioned above, the amount of toner recovered per unit time by the transport component decreases compared to when the motor is driven continuously. As a result, there is a problem that toner may not be completely removed from the surface of the photoreceptor drum, potentially leading to clogging.

[0029] To resolve the above problem, one could consider controlling the motor to maintain a constant rotational speed, but this has the drawback of increasing the processing load related to motor control. Specifically, one could consider implementing feedback control, which controls the motor to maintain a constant rotational speed based on the motor's rotational speed. In this feedback control, pulses output by a detection unit that detects the motor's rotational speed, such as an encoder, are acquired, and the motor's rotational speed is calculated from the acquired pulses. However, if the above feedback control is performed every time a pulse is acquired from the detection unit, the processing load tends to increase. For example, if the period of the pulses output by the detection unit is several kHz, the above feedback control would have to be performed thousands of times per second.

[0030] In contrast, in this embodiment, the motor control system 100 of the image forming apparatus 10, described below, performs processing that makes it possible to reduce the processing load related to motor control while keeping the motor's rotation speed constant, thereby realizing a motor control system 100 and a motor control method.

[0031] Specifically, the ROM 5B of the control device 5 has a program pre-stored in it that causes the CPU 5A to execute the feedback control described below (see Figure 5). This program may be recorded on a computer-readable recording medium such as a CD, DVD, or flash memory, and read from the recording medium and installed in the storage unit 8.

[0032] The control device 5 (motor control system 100), as shown in Figure 3, includes a first acquisition unit 51, a calculation unit 52, and a control unit 53. Specifically, the control device 5 executes the program stored in the ROM 5B using the CPU 5A. As a result, the control device 5 functions as the first acquisition unit 51, the calculation unit 52, and the control unit 53.

[0033] The first acquisition unit 51 acquires pulses output by a detection unit 91 that detects the rotational speed of a motor 92 that rotates a transport body (in this case, a screw 363) for transporting the toner to be removed (waste toner or transfer residue toner). In this embodiment, the detection unit 91 is an encoder attached to the motor 92, more specifically a rotary encoder.

[0034] The calculation unit 52 calculates the rotational speed of the motor 92 based on the pulses acquired from the first acquisition unit 51 at a specific period P1 (see Figure 6) that is longer than the period of the pulses output by the detection unit 91. Specifically, the calculation unit 52 waits for a specific period P1 without measuring the pulse frequency, measures the pulse frequency acquired by the first acquisition unit 51 after the specific period P1 has elapsed, and then waits again for a specific period P1 after the measurement. This series of processes is repeated. The calculation unit 52 may also repeat the following series of processes. In this series of processes, the operation of the first acquisition unit 51 is stopped for a specific period P1, the operation of the first acquisition unit 51 is started to measure the pulse frequency after the specific period P1 has elapsed, and then the operation of the first acquisition unit 51 is stopped again for a specific period P1 after the measurement. Here, since the pulse frequency is proportional to the rotational speed of the motor 92, the calculation unit 52 effectively calculates the rotational speed of the motor 92. Of course, the calculation unit 52 may also calculate the rotational speed of the motor 92 itself.

[0035] In this embodiment, the specific period P1 is several seconds long. The specific period P1 is any period that allows the motor 92's rotational speed to be kept constant by feedback control, and is preferably 5 seconds or less, and more preferably between 1 second and 5 seconds. Of course, the specific period P1 is any period longer than the period of the pulse output by the detection unit 91, so it does not have to be several seconds long, but it is preferable that it be several seconds long in order to reduce the processing load on the motor 92 control as much as possible.

[0036] The control unit 53 controls the motor 92 so that its rotational speed remains constant, based on the rotational speed of the motor 92 calculated by the calculation unit 52. In this embodiment, the control unit 53 controls the motor 92 so that its rotational speed remains constant at a preset reference speed, based on the frequency of the pulse output by the detection unit 91 measured by the calculation unit 52.

[0037] In this embodiment, the control unit 53 controls the motor 92 using PWM (Pulse Width Modulation). Specifically, the control unit 53 determines the duty cycle of the control signal based on the rotational speed calculated by the calculation unit 52, for example, by referring to data pre-stored in the ROM 5B (see Figure 4). Here, the control signal is a binary signal that instructs the on / off switching of the voltage supplied to the motor 92 from the power supply (not shown).

[0038] In Figure 4, "Detection Result" represents the measurement result of the pulse frequency output by the detection unit 91 by the calculation unit 52, or in other words, the measurement result of the rotational speed of the motor 92 by the calculation unit 52. Also in Figure 4, "Correction Rate" represents the correction rate based on the duty cycle of the current control signal. For example, if the duty cycle of the current control signal is 50%, and the "Correction Rate" is 10%, then the duty cycle of the control signal is determined to be 50% + 10% = 60%.

[0039] In Figure 4, "lower speed error" indicates that the rotational speed of motor 92 is lower than the lower limit of the normal speed range, and "upper speed error" indicates that the rotational speed of motor 92 is higher than the upper limit of the normal speed range. If the "correction rate" indicates "lower speed error" or "upper speed error," the control unit 53 stops motor 92. In this case, the control unit 53 may also notify the user that an error has occurred, for example, via the operation display unit 7.

[0040] In this embodiment, the control unit 53 controls the motor 92 by determining the duty cycle of the control signal so that the rotational speed of the motor 92 falls within the range of a reference speed. In other words, the control unit 53 controls the motor 92 by determining the duty cycle of the control signal so that the rotational speed of the motor 92 (frequency of the pulse output by the detection unit 91) falls within a predetermined range (here, 300 to 400 Hz).

[0041] [2] Example of motor control system operation Hereinafter, with reference to Figure 5, an example of the motor control method of this embodiment will be described along with an example of the processing procedure performed by the control device 5 (motor control system 100) in the image forming apparatus 10. Here, steps S11, S12, ... represent the processing procedure (step) numbers performed by the motor control system 100. This processing is started when the cleaning device 36 removes the toner remaining on the surface of the photoreceptor drum 31.

[0042] <Step S11> First, the first acquisition unit 51 sets the duty cycle of the control signal to the initial duty cycle. Here, the initial duty cycle is set according to the reference speed of the rotational speed of the motor 92 and is stored in the ROM 5B beforehand, for example.

[0043] <Step S12> Next, the calculation unit 52 waits without measuring the pulse frequency for a specific period P1 (for example, 1 second). The calculation unit 52 may also stop the operation of the first acquisition unit 51 during the specific period P1.

[0044] <Step S13> When a specific period P1 has elapsed, the first acquisition unit 51 acquires a pulse from the detection unit 91. Note that if the calculation unit 52 stops the operation of the first acquisition unit 51, step S13 may always be executed.

[0045] <Step S14> Next, the calculation unit 52 calculates the rotational speed of the motor 92 based on the pulses acquired by the first acquisition unit 51. Specifically, the calculation unit 52 indirectly calculates the rotational speed of the motor 92 by measuring the frequency of the pulses acquired by the first acquisition unit 51.

[0046] <Step S15> Next, the control unit 53 determines the duty cycle of the control signal by referring to the data shown in Figure 4, based on the rotational speed of the motor 92 (in this case, the pulse frequency) calculated by the calculation unit 52.

[0047] <Step S16> Then, the control unit 53 performs feedback control of the motor 92 by PWM control of the motor 92 using the duty cycle control signal determined in step S15. This controls the motor 92 so that its rotational speed remains constant.

[0048] <Step S17> Subsequently, steps S12 to S16 are repeated until the toner removal process by the cleaning device 36, i.e., cleaning, is completed (step S17: No). When cleaning by the cleaning device 36 is completed (step S17: Yes), the operation of the motor control system 100 also ends.

[0049] The operation of the motor control system 100 will be described below with reference to Figure 6. First, the operation of the motor control system 100 starts at time t0. At the start of operation of the motor control system 100, the control unit 53 sets the duty cycle of the control signal to the initial duty cycle (in this case, 50%).

[0050] Next, at time t1, after a specific period P1 (for example, 1 second) has elapsed from time t0, the calculation unit 52 measures the frequency of the pulse output from the detection unit 91. Then, the control unit 53 determines the duty cycle of the control signal based on the measured pulse frequency. In this case, since the measured pulse frequency is 350 Hz, the control unit 53 refers to the data shown in Figure 4, determines that the correction rate is 0%, and maintains the current duty cycle (in this case, 50%) without changing it.

[0051] Next, at time t2, after a specific period P1 has elapsed from time t1, the calculation unit 52 measures the frequency of the pulse output from the detection unit 91. Then, the control unit 53 determines the duty cycle of the control signal based on the measured pulse frequency. In this case, since the measured pulse frequency is 250 Hz, the control unit 53 refers to the data shown in Figure 4, determines that the correction rate is 10%, and changes the current duty cycle to 50% + 10% = 60%.

[0052] Next, at time t3, after a specific period P1 has elapsed from time t2, the calculation unit 52 measures the frequency of the pulse output from the detection unit 91. Then, the control unit 53 determines the duty cycle of the control signal based on the measured pulse frequency. In this case, since the measured pulse frequency is 350 Hz, the control unit 53 refers to the data shown in Figure 4 and determines that the correction rate is 0%, and maintains the current duty cycle (60% in this case) without changing it.

[0053] Subsequently, when the motor control system 100 finishes operation at time t4, the control unit 53 updates the initial duty cycle to the duty cycle at the end of operation. Here, the initial duty cycle is updated from 50% to 60%.

[0054] After the motor control system 100 has finished operating, when it starts operating again at time t5, the control unit 53 sets the duty cycle of the control signal to the initial duty cycle (in this case, 60%). In other words, the control unit 53 sets it to the duty cycle at the end of the previous motor control system 100 operation. In other words, in this embodiment, when the control unit 53 starts driving the motor 92, it starts driving the motor 92 at the rotational speed at which the motor 92 was stopped the previous time. This has the advantage that the motor 92 can be driven with the same operating load as the previous toner collection operation load, so that the rotational speed of the motor 92 does not vary as much each time the motor 92 is driven.

[0055] Next, at time t6, after a specific period P1 has elapsed from time t5, the calculation unit 52 measures the frequency of the pulse output from the detection unit 91. Then, the control unit 53 determines the duty cycle of the control signal based on the measured pulse frequency. In this case, since the measured pulse frequency is 250 Hz, the control unit 53 refers to the data shown in Figure 4, determines that the correction rate is 10%, and changes the current duty cycle to 60% + 10% = 70%.

[0056] Next, at time t7, after a specific period P1 has elapsed from time t6, the calculation unit 52 measures the frequency of the pulse output from the detection unit 91. Then, the control unit 53 determines the duty cycle of the control signal based on the measured pulse frequency. In this case, since the measured pulse frequency is 150 Hz, the control unit 53 refers to the data shown in Figure 4, determines that a lower limit speed error has occurred, and stops the motor 92.

[0057] As described above, in the motor control system 100 according to this embodiment, the rotational speed of the motor 92 is calculated at a specific period P1 that is longer than the period of the pulse output by the detection unit 91. Then, the motor control system 100 according to this embodiment controls the motor 92 so that the rotational speed of the motor 92 remains constant based on the calculated rotational speed of the motor 92. For this reason, the motor control system 100 according to this embodiment can easily reduce the processing load related to the control of the motor 92 compared to the case where the rotational speed of the motor 92 is calculated each time a pulse is acquired from the detection unit 91. Furthermore, in the motor control system 100 according to this embodiment, the motor 92 is controlled so that the rotational speed of the motor 92 remains constant at each specific period P1. For this reason, it is easier to keep the rotational speed of the motor 92 constant, and it is easier to reduce the possibility that toner may not be completely removed from the surface of the photoreceptor drum 31, making it prone to toner clogging.

[0058] [3] Variant Figure 7 is a block diagram showing the configuration of an image forming apparatus 10 equipped with a motor control system 100A according to a modified embodiment. In this modified embodiment, the motor control system 100A further comprises a second acquisition unit 54, which is different from the motor control system 100 according to the embodiment. In the following, the points that are common with the motor control system 100 according to the embodiment will not be explained.

[0059] The second acquisition unit 54 acquires parameters indicating the remaining amount of toner that has been transported. For example, the second acquisition unit 54 is a timer that measures the elapsed time since the toner was replaced with an unused toner, thereby acquiring the elapsed time as a parameter. Alternatively, the second acquisition unit 54 is a remaining amount sensor located in the toner collection container that detects the remaining amount of toner that has been transported, thereby acquiring the remaining amount as a parameter.

[0060] In this modified example, the control unit 53 changes a specific period P1 according to the parameters acquired by the second acquisition unit 54. For example, the control unit 53 lengthens the specific period P1 the shorter the elapsed time, and shortens the specific period P1 the longer the elapsed time. Also, for example, the control unit 53 lengthens the specific period P1 the larger the remaining amount, and shortens the specific period P1 the smaller the remaining amount.

[0061] Hereinafter, with reference to Figure 8, an example of the motor control method of this modified model will be described along with an example of the processing procedure performed by the motor control system 100A according to this modified model. Here, steps S11, S12, ... represent the processing procedure (step) numbers performed by the motor control system 100A. This processing is started when the cleaning device 36 removes the toner remaining on the surface of the photoreceptor drum 31. Steps S11 to S17 are the same as the operation of the motor control system 100 according to the embodiment, so their explanation is omitted here.

[0062] Steps S18 and S19, shown below, are executed, for example, between step S11 and step S12. Steps S18 and S19 may be executed before step S11, or they may be executed in parallel with step S11.

[0063] <Step S18> The second acquisition unit 54 acquires parameters indicating the remaining amount of toner that has been transported.

[0064] <Step S19> Next, the control unit 53 changes a specific period P1 according to the parameters acquired by the second acquisition unit 54.

[0065] As described above, in this modified example, a specific period P1 is changed according to the remaining amount of toner that has been transported. Therefore, this modified example has the advantage that it is easy to set an appropriate specific period P1 that achieves both a reduction in the processing load related to the control of the motor 92 and a constant rotational speed of the motor 92. For example, when the remaining amount of toner that has been transported is small, the driving load on the motor 92 required to transport the toner is small. Therefore, by making the specific period P1 relatively long, it becomes easier to reduce the processing load related to the control of the motor 92 while keeping the rotational speed of the motor 92 constant. On the other hand, when the remaining amount of toner that has been transported is large, the driving load on the motor 92 required to transport the toner is large. Therefore, by making the specific period P1 relatively short, it becomes easier to keep the rotational speed of the motor 92 constant. In this embodiment, the control unit 53 updates the initial duty cycle to the duty cycle at the end of operation of the motor control system 100, but it is not necessary to update the initial duty cycle.

[0066] In this embodiment, the control unit 53 may lengthen the specific period P1 when the correction rate is 0% in the process of determining the duty cycle, that is, when the duty cycle in PWM control is not updated. For example, if the specific period P1 at the time of execution of the process of determining the duty cycle is 1 second, the control unit 53 may set the specific period P1 to 1.5 seconds or the like for subsequent executions. Furthermore, the control unit 53 may lengthen the specific period P1 with each process of determining the duty cycle as long as the situation of not updating the duty cycle continues. This has the advantage of making it easier to reduce the processing load related to the control of the motor 92 while keeping the rotation speed of the motor 92 constant. However, it is preferable to set an upper limit for the specific period P1 within a range in which it is possible to keep the rotation speed of the motor 92 constant. In addition, the control unit 53 may return the specific period P1 to its original value when the duty cycle is updated.

[0067] [Notes on the invention] The following is an overview of the invention extracted from the above-described embodiments. Note that each configuration and processing function described below can be selected and combined as desired.

[0068] <Note 1> A first acquisition unit acquires pulses output by a detection unit that detects the rotation speed of a motor that rotates a transport body for transporting toner to be removed, A calculation unit that calculates the rotational speed of the motor based on the acquired pulses at a specific period longer than the period of the pulses, The system includes a control unit that controls the motor so that the rotation speed of the motor remains constant based on the rotation speed calculated by the calculation unit, Motor control system.

[0069] <Note 2> The control unit controls the motor using PWM. The motor control system described in Appendix 1.

[0070] <Note 3> The control unit, if it does not update the duty cycle in the PWM control, lengthens the specific period. The motor control system described in Appendix 2.

[0071] <Note 4> The system further includes a second acquisition unit that acquires at least one of the following parameters: the elapsed time since the toner was used and the remaining amount of the toner. The control unit changes the specific period according to the parameter. A motor control system as described in any one of the appendices 1 to 3.

[0072] <Note 5> When the control unit starts driving the motor, it starts driving the motor at the rotational speed at which the motor was stopped last time. A motor control system as described in any one of the appendices 1 to 4.

[0073] <Note 6> An acquisition step involves acquiring a pulse output by a detection unit that detects the rotation speed of a motor that rotates a transport body for transporting the toner to be removed, and A calculation step of calculating the rotational speed of the motor based on the acquired pulses at a specific period longer than the period of the pulses, A control step includes controlling the motor so that its rotational speed remains constant, based on the rotational speed calculated in the calculation step, Motor control method. [Explanation of symbols]

[0074] 100 Motor Control System 363 Screw (conveyor) 51 First acquisition part 52 Calculation Section 53 Control Unit 54 Second acquisition part 91 Detection unit 92 Motor P1 Specific period

Claims

1. A first acquisition unit acquires pulses output by a detection unit that detects the rotation speed of a motor that rotates a transport body for transporting toner to be removed, A calculation unit that calculates the rotational speed of the motor based on the acquired pulses at a specific period longer than the period of the pulses, The system includes a control unit that controls the motor so that the rotation speed of the motor remains constant based on the rotation speed calculated by the calculation unit, Motor control system.

2. The control unit controls the motor using PWM. The motor control system according to claim 1.

3. The control unit, if it does not update the duty cycle in the PWM control, lengthens the specific period. The motor control system according to claim 2.

4. The system further includes a second acquisition unit that acquires a parameter indicating the remaining amount of the toner that has been transported, The control unit changes the specific period according to the parameter. A motor control system according to any one of claims 1 to 3.

5. When the control unit starts driving the motor, it starts driving the motor at the rotational speed at which the motor was stopped last time. A motor control system according to any one of claims 1 to 3.

6. An acquisition step involves acquiring a pulse output by a detection unit that detects the rotation speed of a motor that rotates a transport body for transporting the toner to be removed, and A calculation step of calculating the rotational speed of the motor based on the acquired pulses at a specific period longer than the period of the pulses, A control step includes controlling the motor so that its rotational speed remains constant, based on the rotational speed calculated in the calculation step, Motor control method.

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